fix: initialise image_upload variable

app.py

@@ -55,6 +55,7 @@ This is OCR-free Document Understanding Transformer nicknamed 🍩. It was fine-
 The original 🍩 implementation can be found on: https://github.com/clovaai/donut
 ''')
 
+image_upload = None
 with st.sidebar:
     information = st.radio(
     "What information inside the are you interested in?",